Many foamable personal care compositions are water-based liquids that include one or more synthetic cleansing, i.e., detersive, surfactants commonly known as “syndet” and herein alternatively referred to as “synthetic surfactant” or “cleansing surfactant”. The compositions are commonly oil-in-water emulsions in which a surfactant-containing aqueous phase is combined with an oil phase and other composition ingredients, e.g., volatiles. Creating concentrates (used, for example, as pre-mixes) with conventional water-based liquid detergents can be problematic in that the reduced amount of water in a concentrate can give rise to products that are prone to gel formation or crystallization and, as a result, such concentrates are too viscous to be easily applied or diluted, OCCs are desirably foamable fluid compositions having a continuous oil phase, and which offer potential advantages over conventional water-based compositions in one or more areas, e.g., processing, concentrate formation. As discussed in WO 2015/014604 to Tsaur et al., various oil-based personal care compositions are disclosed. These include U.S. Pat. No. 4,673,526 to Zabotto; U.S. Pat. No. 8,063,005 to Kalidindi; U.S. Pat. No. 6,620,773 to Stork; U.S. Pat. No. 6,524,594 to Santora; and U.S. Publication No. 2005/0158351 A1 to Subramanian.
As noted in WO 2015/014604 to Tsaur, formulating continuous oil phase compositions with desirable phase stability has been problematic. As a disperse phase in oil, solid surfactant tends to separate over time, which can form a layer of particles at the bottom and oil at the top. This tendency increases when larger or heavier particles are used. Conventional stabilization routes, e.g., use of viscosity modifiers and thickeners, can interfere with surfactant release in use, which in turn can affect foam formation and lathering. WO 2015/014604 to Tsaur addresses these issues by using relatively small amounts of fatty acid soap crystals to stabilize synthetic surfactant in the oil phase. At the pH ranges used in compositions of our invention (e.g., 3.0 to 6.5, preferably 4.0 to 6.0) such crystals do not form and indeed compositions of our invention are free of the fatty acid soap crystal defined in the Tsaur application. Rather, compositions of our invention are prepared by a novel process involving low shear rates and a slow cooling rate.
The present invention relates to non-aqueous oil continuous pre-mix compositions comprising fatty acyl isethionate surfactants (e.g., cocoyl isethionate), which pre-mixes may be used in a final OCC (in theory, the pre-mix can be used as “final” OCC if desired) or which pre-mixes may be used as ingredients in formulation of other compositions. The pre-mix compositions are desirable because compositions comprising fatty acyl isethionate surfactants lather well, are mild to the skin and have good emollient properties.
Preparation of OCCs containing fatty acyl isethionate surfactants (when these surfactants are produced by the direct esterification of fatty acid and isethionate, they are commonly referred to as “DEFI” surfactants) can be problematic. Specifically, it is important to obtain fatty acyl isethionate (FAI) particles having an average particle size of 100 microns or below, preferably less than 75 microns, more preferably less than 50 microns. Typically, such small size particles are not perceived as “gritty” by the consumer. It is also believed that the small particles are more readily pumpable and thus make the pre-mix easier to incorporate into a final composition or into containers during processing.
One way to ensure particles having a small average particle size are obtained is through in-line wet milling. This process comprises milling larger size FAI particles which have been combined with oil using specialized ultra high shear equipment (up to 100,000 s−1) designed to reduce average particle size below 100 microns. During production of OCC, this may then be followed by subsequent addition of other solid surfactants (e.g., betaine and/or glycinate powders). Polymer and soap are typically further added as structurants to the main mixer. The wet milling process is energy intensive (high shear transferred to product), leading to product temperature increase and requiring product cooling. The process can be expensive as well as it requires introducing an in-line wet mill and a heat exchanger to the mixer design. Further, it is difficult to control the particle size distribution (e.g., particle span) when using wet milling process.
Applicants have now found that small average particle size FAI (having average particle size of 100 microns or less, also having a narrow particle size distribution) can be formed in a FAI/oil premix (to be used in the final OCC) using a specific in-situ process where (1) heated oil and molten FAI (obtained, for example, from the directly esterified fatty acyl isethionate or “DEFI”, formed at end of a DEFI reaction) are mixed; (2) the mixture is heated to ensure liquid phase formation; and (3) the mixture is cooled in a controlled manner (e.g., 0.5 to 5° C. per minute) to ensure that surfactant particles of average particle size of 100 microns or less are formed. Using a controlled cooling process, it is possible to make small average particle size particles at relatively low shear rate (e.g., 10 to under 1000 sec−1; shear rate is estimated based on the physical dimensions of the reactor/homogenizer and rotation in revolutions per minute or RPM; shear rates of our invention were estimated at about 95-100 sec−1 at 350 RPM). The shear rate during step c) and/or d) is 10 to 1000 sec−1.
In addition, in the process of our invention, water is driven off during the DEFI reaction (high temperature reaction occurring at 200 to 245° C.) and no water is re-added as this would be unnecessary and inefficient. Although there is a small amount of water that comes in with the initial raw materials, preferably the final composition contains less than 2%, or 1% or less, or 0.5% or less (0 to 0.5% by wt.) water.
The present invention is directed to the novel small average particle size, narrow particle distribution FAI in oil compositions themselves. It is further directed to a novel process for obtaining the novel compositions.
The process of the invention for forming the pre-mix relates typically to combination of FAI and oil, although optional structurants (e.g., soap) and emulsifiers may be part of the process for forming the pre-mix. The pre-mix (containing FAI and oil, optional structurant and optional emulsifier) can be later combined with other ingredients to form final OCC. This intermediate pre-mix is in effect a raw material which can be made, and then stored and used as needed to make the “final” OCC (as noted, if desired the intermediate pre-mix may be the final OCC) or to make other cleaning formulations. It is noted that, if FAI is made by DEFT process, the pre-mix can comprise both the FAI formed from the reaction as well as unreacted fatty acid, unreacted isethionate salt (e.g., sodium isethionate), catalyst (if employed), and any trace impurities which might be present in the raw materials.
Processes for making fatty acid esters of salts of isethionate (e.g., by reacting fatty acid with sodium salt of hydroxyl alkyl sulfonates to form, for example, sodium cocoyl isethionate or “SCI”) are not new (the direct esterification of fatty acid and the sodium salt are, as noted, what is referred to as “DEFT” reaction). U.S. Pat. No. 6,069,262 to Walele et al., WO 98/42658, U.S. Pat. No. 3,029,264 to Voorburg and many other references disclose such processes for example.
None of the references relating to formation of salt of acyl isethionate disclose in-situ processes wherein, at the end of a process for making FAI (e.g., DEFI process), molten FAI and oil (optionally heated) are combined, the mixture is further heated to ensure liquid phase formation, and this mixture is then cooled in a controlled manner (e.g., defined rate of temperature drop per minute) to obtain FAI crystals which have an average particle size of 100 microns or less, and further have a narrow particle size distribution (e.g., span, as defined below, of less than 4.5, preferably less than 4, more preferably less than 3). Compositions made by such process are also not disclosed.
Many references disclose compositions containing oils or compositions containing fatty acyl isethionate or compositions containing both but, again, none of these disclose a specific in-situ process for making a premix comprising FAI and oil which process involves cooling FAI (plus any unreacted fatty acid, unreacted salt of isethionate, catalysts (if employed), and trace impurities, if any, which may be the by-product of the invention) and oil (in addition to any optional structurant and/or emulsifier) which have been combined as noted above in a controlled manner to ensure small average particle size FAI particles in oil, wherein the particles further have a narrow particle size distribution (defined by span); and further wherein reaction is at low shear (<1000 sec−1) and no water is added during the reaction. Preferably, the final composition of our invention have less than 2%, e.g., 0 to less than 2% by wt. water.
WO 2002/079717 to Merz, for example, appears to disclose liposome forming aqueous bath which may contain oil (claim 5) and isethionate (claim 6) but the controlled cooling, low shear process of the invention and formation of small average particle size, narrow particle distribution FAI does not appear to be disclosed.
U.S. Pat. No. 8,111,824 to Dasgupta et al.; U.S. 2012/0094884, U.S. 2012/0094885, and U.S. 2010/0210500 all to Liu; and U.S. 2008/0153727, U.S. 2008/0513729 and U.S. 2008/0153730, all to Tsaur et al., all disclose compositions with DEFI and oils in the composition. There is no disclosure of a FAI in oil premix, or of a specific process for making such premix and ensuring in-situ formation of small average particle size FAI further having narrow particle size distribution.
Similarly, US 2004/0136942 to Yamazaki, WO 03/051319 to Beirsdorf and WO 00/21492 to Johnson and Johnson disclose compositions which may have DEFI and oils, but there is no teaching of specific FAI-in-oil premix concentrates or processes to form these and ensure formation of small average particle size FAI further having narrow particle size distribution.
WO 99/04751 to Puvvada et al. (Unilever) discloses compositions where the level of oil-emollient is equal to or in excess of level of surfactant. First, no FAI is even specified.
Further, there is again no disclosure of the specific process of our invention or of the compositions of our invention.
EP0585071 to Hoechst discloses a process for making sodium acylisethionate which comprises directly esterifying fatty acid and hydroxyalkanesulfonic acid at a temperature of about 180°-240° C., adding paraffin to the reaction mixture, distilling excess fatty acid, cooling preferably to below 180° C., and adding more fatty acid and anhydrous metal alkali salts. No information is given about rate of cooling and, from Example 1, it is seen that at about 100° C., ice water is added and there is rapid cooling. This differs significantly from our process where (1) there is a constant and controlled rate of cooling and (2) where excess cooling leads to significantly higher particle size distribution (see our Example 3). Average particle size and particle distribution, and the processing effect on these parameters is unrecognized and unmentioned in the reference.
WO 2015/014604 noted above discloses use of fatty acid soap crystals to stabilize surfactant. At the pH levels used in compositions of our invention, such fatty acid soap crystals do not form.
In related WO 2015/014667, stabilization is achieved either by using pre-aggregated solid surfactants and/or solid surfactant particles that are aggregated in situ by addition of water. Particles of the invention are not pre-aggregated, nor is water added in our DEFT reaction since such would add additional complexity and inefficiency.
US 2014/155309 relates to solid personal care bars. The compositions utilize synthetic waxes which are solid at room temperature (e.g., 20-25° C.). Oils used in the compositions of our invention are preferably liquid at room temperature.